Scarlet pimpernel

Description
Annual seed-propagated weed with a thin taproot, opens flowers before rain. A. arvensis was used as a medicinal plant against mental diseases.

Characteristic Features
Sessile, opposite leaves.
Orange-red flowers.
Globose fruits.

Cotyledons
Cotyledons spatulate, acuminate, smooth-margined, sprinkled underneath.

Stems
Prostrate, only slightly ascending, not very ramified, square in cross-section, hairless, up to 15 cm (5.9 inch).

Leaves
Round oval to broad ovate, deep green, glossy, with dark dots underneath, entire margin, nearly sessile, crosswise opposed or coroniform in groups of three.